Using Xenopus as a model system for an undergraduate laboratory course in vertebrate development at the University of Bordeaux,France

The goal of this laboratory course is to introduce vertebrate developmental biology to undergraduate students, emphasizing both classical and contemporary aspects of this field. During the course, the students combine the use of living Xenopus laevis material with active tutorial participation, with the aim of illustrating how the fertilized egg can generate the diversity of cell types and complexity of pattern seen only a few days later in the embryo. Special emphasis is given to the observation and manipulation of living material. The laboratory course includes a comprehensive analysis of both oogenesis and early development and is divided into two overlapping parts that combine tutorial and practical approaches. The first part is devoted to oogenesis; oocytes are sorted out, allowed to mature in vitro and observed in histological section. In the second part, students perform an in vitro fertilization of Xenopus eggs and a mesoderm and neural induction assay of animal cap explants. Successful induction of the explants is confirmed by morphological, histological and molecular analyses. Finally, the students observe and comment on selected slides to illustrate the organization of the body plan of the amphibian embryo at an early stage of organogenesis.     

Cambrian stem-group annelids and a metameric origin of the annelid head

The oldest fossil annelids come from the Early Cambrian Sirius Passet and Guanshan biotas and Middle Cambrian Burgess Shale. While these are among the best preserved polychaete fossils, their relationship to living taxa is contentious, having been interpreted either as members of extant clades or as a grade outside the crown group. New morphological observations from five Cambrian species include the oldest polychaete with head appendages, a new specimen of Pygocirrus from Sirius Passet, and an undescribed form from the Burgess Shale. We propose that the palps of Canadia are on an anterior segment bearing neuropodia and that the head of Phragmochaeta is formed of a segment bearing biramous parapodia and chaetae. The unusual anatomy of these taxa suggests that the head is not differentiated into a prostomium and peristomium, that palps are derived from a modified parapodium and that the annelid head was originally a parapodium-bearing segment. Canadia, Phragmochaeta and the Marble Canyon annelid share the presence of protective notochaetae, interpreted as a primitive character state subsequently lost in Pygocirrus and Burgessochaeta, in which the head is clearly differentiated from the trunk.     

Genomic analysis of the phosphotransferase system in Clostridium botulinum

Clostridium botulinum is capable of fermenting carbohydrates, but there have been no detailed studies of the uptake of sugars and related substrates. In bacteria, a common and often predominant system of carbohydrate uptake is the phosphoenolpyruvate (PEP)-dependent phosphotransferase system (PTS). This multi-protein complex catalyses a group translocation involving both uptake and phosphorylation of carbohydrates, and is also known to play an important role in environmental sensing and metabolic regulation. The genome of C. botulinum encodes 15 PTSs which have a similar domain structure to the PTS in other bacteria. Based on phylogenetic relationships and analysis of gene clusters, the C. botulinum PTS appears to be involved in the uptake of hexoses, hexose derivatives and disaccharides. C. botulinum also contains the components of PTS-associated regulatory mechanisms which have been characterised in other bacteria. It therefore seems likely that the PTS plays a significant, and previously unrecognised, role in the physiology of this bacterium.     

Diadenosine polyphosphates and the control of cyclic AMP concentrations in isolated rat liver cells.

Extracellular diadenosine polyphosphates (Ap(n)A), through their interactions with appropriate P(2) receptors, influence a diverse range of intracellular activities. In particular, Ap(4)A stimulates alterations in intracellular calcium homeostasis and subsequent activation of glycogen breakdown in isolated liver cells. Here we show that, like ATP, Ap(4)A and other naturally occurring diadenosine polyphosphates attenuate glucagon-stimulated accumulation of cyclic AMP in isolated rat liver cells. The characteristics of Ap(4)A- and ATP-dependent modulation of glucagon-stimulated cyclic AMP accumulation are similar. These results are discussed in the context of the repertoire of intracellular signalling processes modulated by extracellular nucleotides.     

Phylogeny of Henicopidae (Chilopoda: Lithobiomorpha): a combined analysis of morphology and five molecular loci

Abstract. Relationships in Henicopidae, the dominant southern temperate clade of Lithobiomorpha, are appraised based on parsimony analysis of forty-nine morphological characters and sequence data from five loci (nuclear ribosomal RNAs 18S and 28S, mitochondrial ribosomal RNAs 12S and 16S, protein-coding mitochondrial cytochrome c oxidase I). A combined analysis of these data used direct character optimization, and tested stability of hypotheses through parameter-sensitivity analysis. The morphology dataset highlighted the mandibles as a source of new characters. Morphology, as well as the most congruent parameters for the sequence data and combined analysis, resolved Zygethobiini within Henicopini. Groups retrieved by combined analysis of the sequences and combination with morphology for all parameters include Anopsobiinae/Henicopinae, Lamyctes + Lamyctinus + Henicops , Paralamyctes ( Paralamyctes ), and a clade that groups the southeastern Australian/New Zealand Paralamyctes ( Haasiella ) and P . ( Thingathinga ). Paralamyctes (including Haasiella ) is a Gondwanan clade in the most congruent cladograms based on all molecular data and combination with morphological data. Biogeographic analysis of subtrees for Paralamyctes resolved the interrelationships of Gondwana as (Patagonia ((New South Wales + southeastern Queensland) ((Tasmania) (southern Africa + India) (New Zealand + north Queensland)))).